Fix rusted drain in tile shower

Removing the hair trap caused the screws to break off like they were made of clay. Now I've got a hideously rusted (cast iron?) open drain set into the tile shower bottom, and no way to attach the hair trap. Is this a matter of choosing between (1) tearing out the shower and rebuilding the whole thing, or (2) sticking the hair trap down with caulk?

A drill, an EZout and some new (preferably) stainless steel screws, and you should be back in operation. You'd also probably want to use something like PBlaster to try to lubricate and maybe loosen up the screws, but if they are steel and old, they're likely pretty intimate with the CI drain! If there's anything sticking up, after letting it soak in PBlaster overnight, you might try using a Vice-Grip to unscrew them. You could also just drill them out and rethread the holes, but I'd try to get them out first.

Thanks Jim, I had sort of mentally skipped over that option. I guess it's worth a try, though I was imagining that with everything being so soft/rusted that it would be pretty difficult to drill out and extract such a skinny screw. Any good fall-back options in the event that I can't extract or drill out the old screws?

Well, no joy from PBlaster and vise grips ... only managed to shear off the 1/8" screw part that was protruding above the rust. So next step would be to drill out the screws, but the rust has taken away so much of the metal that there's only 1/16" of (heavily rusted) metal on the outside of the screw. Once I drill and rethread, it looks like it will just collapse. What would you do in this situation?

Not really. I guess it's difficult to see in the picture, but the cast iron was molded with two little bumps that protrude from the inner circumference, and that's where the screw holes were placed. These bumps are mostly rusted away, so there's no other place to put screw holes with the same distance between them. I guess there's a chance that I might be able to start drilling out the screws, and angle the hole away from the drain a bit so that it goes into more intact iron.

Well, now that I've brushed off all of the flaky rust scale, it's very clear that drilling/tapping the screw holes is not going to work. There's just not enough metal left around where the hole is supposed to be; by the time I drill and tap it, it would just collapse. So I'm back where I started, which is fresh out of ideas (and ticked off at whoever thought that it was a good idea to put a rust-prone cast iron drain in a concrete/tile shower floor). Is there any other solution, short of tearing the tile and cement out?
See that thin aluminum trim ring that's supposed to be affixed (with grout) to the top of the drain? Would I be able to replace that with a similar ring that includes some little threaded tabs into which I can screw the hair trap/cover? I'll go look around for such a product, but please point me in the right direction if you know of such a product (or have another suggestion).

There is plenty of metal left as long as you only drill out the screw and tap it with the same size screw as in in it now, which you have to do anyway so the screw will fit the drain cover. And, those two bosses are the only place you can put the screws.

Perhaps you can set in a new strainer and grill. Maybe the new strainer can just loosely be fixed in place and attached with nothing more than silicone???

Can you send me the outside diameter of the strainer needed and the inside measurement of the drain and I'll see if any of my strainers fit your drain. I have plenty lying around since often I do not need them installing my linear drains.

Thanks JW, that's very generous! The thin aluminum trim ring (looks to be stuck down with grout) has 3.5" outside diameter, and the removable screen portion is 3.25" in diameter. Are you thinking that I could just stick the screen part down with silicone? That was my original idea, and the screen that I have is sound enough that I can still use it. Or maybe you're describing a sort of retrofit assembly like what I was asking about in post #9 above?

I'm thinking at this point if you can get a new strainer positioned inside the rusted opening. You can use it's grill as a new top. Finding one that sits inside with pressure will leave it accessible for removing.

I'll check my stock. Hang on.

I have a Watts strainer and grill that measures 2 3/4" to 2 7/8" across the outer MPT threads. It would easily slide into a 3 1/4" opening. The top is only 4 1/8" wide and the strainer is the same with two screw locations. Perhaps you can use this inside your old drain and rig up a new top or modify the existing one.

Thanks John, I really appreciate it ... but I think I'd have trouble dealing with the 4 1/8" diameter top and getting it flush with the tiles ... if I'm picturing things correctly, I'd need to cut/chip out tiles from my current 3.5" outside diameter, and I imagine making a total hash of that job. I think I'll just just stick the existing screen down with some caulk and call it a day.